A valve is a key component of a valve mechanism of an engine, and the opening and closing of the valve allow combustible gas to enter a cylinder and waste gas to be exhaled. A hollow valve is lightweight, and the thermal conductivity is effectively improved due to the function of a certain volume of metal sodium sealed in a hollow part of the hollow valve. In the working process of the engine, valve disk parts and a valve seat strike each other frequently and undergo erosion from the high-temperature and high-pressure combustion gas, particularly, a heavy load being applied to valve neck parts. Therefore, the valve must not only have a higher mechanical performance but also requires the internal metal streamline direction to be consistent with its appearance with a fine metallographic structure and a certain fatigue strength.
A hollow valve production method commonly used in China is a solid valve drilling method, which can only be used to get a hollow valve with a hollow stem part but solid disk parts. In addition, the production efficiency and the material utilization rate are low, and waste is caused particularly for the hollow valve formed from a group of revolving bodies with different shapes and sizes.